1. Field of the Invention
The present invention relates to a system for making a search for a document in accordance with a query of a natural language. In particular, the present invention relates to a system and method for making a search for a document suitable to provide a user with a search result for queries of a plurality of matters.
2. Description of the Related Art
Conventionally, there has been well known a system (document search system) for, in accordance with a user's search request (query), making a search for a document (document data) that conforms to the search request from a database. A keyword or natural language is used for the search request. A document search system having applied thereto a technique described in Jpn. Pat. Appln. KOKAI Publication No. 7-182373 (hereinafter, referred to as prior art) is known as such a type of document search system, for example. The prior art is characterized in that an abstract of a searched document is generated as a search result, and a user is provided with the abstract together with the document (original-document). According to the prior art, the user can easily judge the original document provided together with the abstract is based on one's own intention from the provided abstract.
However, in the above-described prior art, it is not presumed that a plurality of matters (matters of the user's interest) are queried by the user's query using a natural language (question sentence). There is a possibility that, if two or more matters such as “teach XX and YY” are included in a query, a plurality of separate documents (hit documents) or abstract are acquired as a search result.
For example, in the case of a query sentence of querying two (a plurality of) matters such as “teach a color and manufacturer of a baggage”, the following hit documents can be obtained in the above described prior art:
a) a document including all words “baggage”, “color”, and “manufacturer”;
b) a document including words “baggage” and “color”;
c) a document including words “color” and “manufacturer”; and
d) a document including words “baggage” and “manufacturer”.
Here, although the document falling under item a) above may be found, such a document is not always found. For example, in some cases, the document falling under item a) above is not found, but only the documents falling under items b) and d) may be found. In this case, the documents falling under items b) and d), respectively, are provided as separate items of information. However, these individual items of information provided are insufficient as an answer to a question.